WASHINGTON  When the United States invaded Iraq last year to disarm Saddam Hussein's regime, there were no weapons of mass destruction in Iraq or any facilities to build them, according to a definitive report released Wednesday.

The 1,000-page report by chief weapons searcher Charles Duelfer, a document that President Bush said would represent the last word on the issue, confirms earlier findings and undermines much of the Bush administration's case about the Iraq weapons threat, though it does say Saddam intended to restart his weapons programs once United Nations sanctions were lifted.

Using the research of the 1,700-member Iraq Survey Group, Duelfer concluded that Saddam ordered his arsenal of chemical and biological weapons destroyed in 1991 and 1992 and halted nuclear weapons development, all in hopes of lifting crippling economic sanctions.

"Saddam Hussein ended the nuclear program in 1991 following the Gulf War," the report states.

The findings were similarly definitive concerning chemical and biological weapons: "Iraq unilaterally destroyed its undeclared chemical weapons stockpile in 1991" and the survey team found "no credible indications that Baghdad resumed production."

The report, released four weeks before the presidential election, immediately became political fodder.

Bush's spokesman said the report justified the decision to go to war. Campaigning in Pennsylvania, Bush defended the decision to invade.

"There was a risk, a real risk, that Saddam Hussein would pass weapons or materials or information to terrorist networks," the president said in a speech in Wilkes Barre, Pa. "In the world after Sept. 11, that was a risk we could not afford to take."

A spokesman for opponent John Kerry said the report "underscores the incompetence of George Bush's Iraq policy."

"George Bush refuses to come clean about the ways he misled our country into war," Kerry spokesman David Wade added.

"In short, we invaded a country, thousands of people have died, and Iraq never posed a grave or growing danger," said Sen. Jay Rockefeller, D-W.Va.

The report resolves disputes about allegations made prior to the U.S. invasion:

• Aluminum tubes that the Bush administration alleged were for nuclear weapons production were, in fact, for making conventional artillery rockets.

• Iraq did not try to buy uranium overseas.

• The team found no evidence that Iraq was developing biological weapons trailers or rail cars. Two trailers found after the war were for producing hydrogen gas for weather balloons.

"The former regime had no formal written strategy or plan for the revival of WMD after sanctions," a report summary says. "Neither was there an identifiable group of WMD policymakers or planners separate from Saddam. Instead his lieutenants understood WMD revival was his goal from their long association with Saddam and his infrequent, but firm, verbal comments and directions to them."

The report's conclusions about Iraq's weapons plans came from interviews with jailed Iraqi officials, including Saddam, who is in U.S. military custody while awaiting an Iraqi war crimes trial. Duelfer quoted Saddam as telling an FBI interrogator "that nuclear weapons were the right of any country that could build them."

The report, which drew on CIA and FBI interrogation reports on Saddam, says he was obsessed with his status in the Arab world, dreaming of weapons of mass destruction to pump up his prestige. And even as the United States fixated on him, he was fixated on his neighboring enemy, Iran.

That is the picture that emerges from interrogations of the former Iraqi leader since his capture last December, according to the report, which gives a first glimpse into what the United States has gleaned about Saddam's hopes, dreams and insecurities.

The report suggests that Saddam tried to improve relations with the United States in the 1990s, yet basked in his standing as the only leader to stand up to the world's superpower.